A quick course on how to make compost, and why you want to…
How to Make Compost – the super Fertilizer!
What is compost?
“Composting” is a man-made process that uses nature’s own biological processes to reduce large amount of organic material to a small amount of usable “compost”, the result of the process. The resulting compost continues to decompose until we are eventually left with “humus”, the end result of decomposition. This end product is important to healthy soil. Although it is essentially inert and no longer able to decay further, it remains a nutrient resource, keeping dissolved minerals in solution ready to be exchanged with hungry root hairs.
Compost also serves as a food source for the living organisms in the soil. Providing a healthy growing medium for the beneficial soil organism helps them keep the pests and diseases in check.
Making compost requires just four things, carbon, nitrogen, air and water. Carbon is supplied by ‘brown’ materials (dried leaves, dried grass, straw, woody plant trimmings, shredded paper),while nitrogen is supplied by ‘green’ materials (fresh grass trimmings, fresh kitchen waste, wilted weeds, etc.). Water is required by the decomposition chemistry, and air is required by the micro-organisms that do all the work.
While compost is relatively low in nutrients, what is available is released slowly, making compost a long-lasting fertilizer and soil conditioner. The compost not only yields its nutrients to your plants, it also feeds the living organisms in your soils that help, or are sometimes required, for healthy plants.
Compost may be made simply by making a pile of yard and kitchen waste. It will decompose slowly, and in a year’s time give you usable compost. This is easy, but slow, and may not have any effect on weeds or disease organisms in the materials.
Proper containers that hold in the heat and moisture, and keep out pests, help the processing at home. Various type of bins used to make compost include commercial plastic garden compost bins in different shapes and styles, wooden compost bins made from discarded pallets, compost bin tumblers (I have two large Kemps). Homemade compost bins can be made from many materials, some as simple as a ring of chicken wire and few stakes.
Rapid compost takes a bit more work, but has the advantages of generating high heat levels within the pile that kill many weed seed and most disease organisms. Some weed and disease species may not be killed, but most are. Rapid composting works on the basis of there being a certain amount of energy that will be released by breaking down the material. The same amount of energy and heat is released whether you burn the pile or slowly decay it. Rapid composting lets microbes do the digestion instead of an actual fire, but the heat is released over a short period of time and causes the pile to heat up to high temperatures.
The other advantages of rapid composting are that large amounts of compost may be made throughout the gardening season in as little as 2 to 3 weeks, and you get exercise turning the pile. Contrary to popular belief, a well tended compost pile does not stink (that is a sign that you are out of balance somewhere), but rather has a pleasant, earthy smell.
The main cause of fouls smells from composting is from lack of aeration. Kitchen wastes compact readily, and if they are not turned and exposed to air, the will go anaerobic. Easy of turning is the biggest concern when selecting a composter. A well balanced, well turned pile will give you a load of compost once a month.
So, the question is – how do we make a balanced compost pile?
Brown to green ratio – In the compost pile, the carbon to nitrogen ratio should be 30:1. Because the bulk and moisture content of brown and green materials, we can simply use equal volumes of each and come pretty close the correct ratio.
Size – Materials should be chopped into 1/2″ to 1 1/2″ pieces.
- Larger sizes have less surface to volume and require longer to decompose
- Smaller than that might lead to matting of the materials. Matting reduces the amount of air and will cause anaerobic bacteria to take over (think sewage smells).
Moisture content -
- A compost pile should be about as wet as a wrung-out sponge; damp, but not sopping wet.
- Over watering the pile also reduces the amount of. air in the pile and will produce the same objectionable smell
- Under-watering slows or stops the bacteria from doing their job
- Water is an important chemical to the composting bacteria.
Keeping the heat on -
- Compost piles will begin to heat up in 24 to 48 hours, and the temperature will rise to 160 degrees with a couple more days.
- This heat is evidenced by the steam that escapes when the pile is turned.
- Not turning the pile often enough may let the heat build up to a point where the micro-organisms are killed, and the cycle will have to start over
- Turn your pile before it fits 160 degree F or the beneficial bacteria will cook off..
- Composting in a bin, possibly with a lid, help retain the heat on cool days.
- A compost thermometer (like this one, also shown on our ‘Tools and Books‘ page) helps you gauge your compost pile’s health.
Turning the pile -
- Turning the pile so the outsides of the pile are moved to the center, and the center moved to the outside helps control the build up of heat.
- Turning makes sure that all the materials are eventually exposed to the high heat needed to kill weed seeds.
- Bins with removable slats make moving or turn the pile easier.
- I also like the tumbler-type composters since here is no shoveling involved; you crank the handle and the materials are mixed.
- The more often you turn the pile, the faster the process goes.
How fast does it happen? -
- If you turn the pile every day, compost will be ready in as little as two weeks,
- Turning every other day takes three weeks.
- Never turn it and it takes a year.
- Once you start your pile, do not add more materials to it. Doing so only makes it take longer to finish. Start a new pile instead (it will be done about the same time, anyway).
Materials you should avoid include soil (just makes it heavy, dense, and no fun to turn), wood ashes (they are alkaline, and our soil is already that way), meat-eaters’ manure (possible diseases), and greasy food leftovers (grease slows decomposition and attracts pests).
So what can go wrong?
- If the pile doesn’t heat up within a day, it is too wet, too dry, or lacking green material.
- If it too wet, spread it to dry or add dry material to absorb some of the moisture.
- If it is too dry, water it until it is evenly moist (some turning here is beneficial to even moisture).
- If neither of these is the case, add more green, nitrogen bearing materials, like lawn clipping or animal manures (NOT from meat-eating animals as it may contain diseases).
- If the pile smell of ammonia, there is too much green material and you are losing valuable nitrogen. Add brown materials like saw dust, shredded paper, etc.
- If you get that sewage smell, the materials have matted together, or are too wet.
A healthy pile has a pleasant smell, steams when turned, and has a white fungus on the material. As it finishes the process, the pile cools and takes on a dark brown, almost black, color. Once all heat production has stopped the compost is ‘finished’ and ready to use in the garden. You can screen the compost through a course wire screen and return any large pieces to the next pile; they will eventually disappear. They are also a good way to inoculate the fresh pile with active bacteria.
So why should you go to all this trouble?
- You are turning ‘waste’ that would go the landfill in to valuable amendments
- By making your own fertilizer, you save money and the oil and energy needed to make commercial chemical fertilizers
- You can make compost in 2 to 4 weeks
- You destroy most weeds and disease organisms
Would yo like to find out more? Here are some other publications about composting you may find handy…
USDA National Agricultural Library, Alternative Farming Systems Information Center – Compost and Composting This site has links to some great resource material.
UCCE ‘Compost in a Hurry‘
North Carolina Cooperative Extension’s list of composting resources